Magnetic thin film recording disks are commonly manufactured by a s of sputtering processes in an environment of low pressure inert gases. A disk is commonly comprised of a substrate made of nickel phosphorus (NiP) or ceramic glass, an optional magnetic seedlayer, a non-magnetic underlayer made of either pure chromium (Cr) or a chrome alloy (CrX), covered by a magnetic layer made of a cobalt (Co)-based alloy. A protective layer made of sputtered carbon is typically used on top of the magnetic layer and an organic lubricant may be used on top of the protective layer.
A seedlayer is used, especially on glass substrates, to control the grain size of the layers subsequently deposited on it. The ideal seedlayer helps to increase the signal to carrier noise ratio of the recording medium. In addition, the seedlayer provides a template to improve the film texture, decrease inter-granular coupling and enhance magnetic properties.
The present invention is directed to the field of magnetic recording media in which a seedlayer includes an aluminum-containing intermetallic nitride for improved performance. Intermetallic alloys are compounds of ordered alloy phases formed between two or more metallic elements where the different atomic species occupy specific sites in the crystal lattice. On a phase diagram an intermetallic alloy appears as an intermediate phase that exists over a narrow range of compositions.
A first aspect of the invention is directed to a magnetic recording medium precursor comprising a substrate and a seedlayer comprising an aluminum-containing intermetallic nitride supported by the substrate. A non-magnetic underlayer may be supported by the seedlayer and a magnetic layer may be supported by the underlayer to create a magnetic recording medium.
Another aspect of the invention is directed to a method for making a magnetic recording medium precursor including depositing a seedlayer, comprising an aluminum-containing intermetallic nitride on a substrate. A non-magnetic underlayer may be deposited over the seedlayer and a magnetic layer may be deposited over the underlayer to create the magnetic recording medium.
The use of an aluminum-containing intermetallic nitride seedlayer provides a buffer layer for the underlayer to grow on. This seedlayer helps refine the underlayer and magnetic layer grain size so to improve the performance of the media. The use of the aluminum-containing intermetallic nitride seedlayer is believed to help develop a favorable in-plane texture in the non-magnetic underlayer and in the magnetic layer itself. The seedlayer is also believed to lead to an increase in the in-plane coercivity and remnant magnetization thus improving the parametric performance of the media.
Deposition of the seedlayer may be accomplished by sputtering. A first sputtering technique reactively sputters an aluminum-containing intermetallic alloy in an atmosphere of argon and nitrogen. The Ar:N atomic ratio can vary widely, such as from about 1:10 to about 1:1. A second sputtering technique uses a sputtering target of a desired intermetallic nitride composition in an atmosphere of argon. The amount of nitrogen in the target will commonly range from about 1 to 50% atomic. Other sputtering gases, such as methane and oxygen, or a combination thereof, may also be used. Other techniques for depositing an aluminum-containing intermetallic nitride as the seedlayer may also be used.